Apparatus for carbonizing coal and the like



Aug. 6, 1929. F. c. GREENE ET AL 1,723,932

APPARATUS FOR CARBONIZING COAL AND THE LIKE Filed 001:. 24, 1925@Green/C1; I, Fila/100165,

Patented ug. 6, 1929.

UNITED STATES PATENT OFFICE.

IFBANK C. GREENE, F WAUKEGAN, ILLINOIS. AND IRVING F. LAU'CKS, 0FSEATTLE, WASHINGTON, ASSIGNORS TO OLD BEN COAL COEPORATION, OF CHICAGO,ILLINOIS,

A CORPGRATION 0F DELAWARE.

APPARATUS FOR CARBONIZING COAL AND THE LIKE.

Application led October 24, 1925.

In Patent No. 1,713,840 granted May 21, 1929, to Irving F. Laucks, thereis disclosed an apparatus for ca1'bonizing-coal at a relatively lowtemperature, which apparatus comprises a screw retort which isinternallyand externally heated. The functions ofthe screw retort are, first, toproduce agitation, circulation or kneading of the particles of coal froma period commencing previous to the softening point and lasting throughthe plastic stage; and, second, to ralse the temperature of the materialbeing treated, means being provided in practice tor regulating thetemperature to eitect the desired results.

Certain operations or reactions occurring prior to the softeningpointand after thel plastic mass has set may be better accomplished byother apparatus than a screw retort. For'example, drying of the. coaland preheating almostlup to the softemng point may be effectively donein less expensive apparatus than a screw retort. Likewise, the coke maybe annealed more economically and to better advantage in a retort aparttrom the screw retort, as the screw tends to abrade the coke and producebreeze or fines. The object of the present invention, theretore, is toprovide, in connectlon. with an improved form of screw retort, lmprovedmeans for treating the coal prior to its 1ntroduct-ion into the screwretort and for treating the coke after it has' been discharged from saidretort. Certain improvements in the screw retort also will be pointedout hereinafter. v n

In the accompanying drawings, Figure 1 is a View, more or lessdiagrammatic, illustrating an apparatus embodying the features of ourinvention, the View being taken in the plane of line. 1-1 of Fig. 2. 0

lfig. 2 is a sectional View taken in the plane ot line 2-2 of Fig. 1.

ln the drawings, 1 denotes a conveyor by means ot' which coalisdischarged int-o a hopper 2. The lumps-ot' coal are preferably, althoughnot necessarily, under one inch in size. rlhe outlet from the hopper 2is controlled by means of a rotary feed gate 3 of well knownconstruction, in order that air may be excluded from the apparatus. Thecoal passing through the feed gage 3 enters an enclined spout a whichdirects the erial No. 64,543.

coal to a drier or preheater 5 of any preferred construction. In theconstruction herein shown the preheater 5 comprises a furnace 6containing a relatively long rotatory drum 7 into one end of which thespout 4t extends. The inlet end of the preheater drum 7 isvslidablysupported to accommodate expansion and contraction of the drum. Thefurnace 6 is preferably heated by means of a gas burner 8 supplied withgas produced in the carbonizing process, the product-s ot combustionbeing"discharged through a stack 9. Within the drum 7 is fixed a devicefor agitating andadvancing the materia-l toward the outlet end of thedrum. l/Vhile the agitating and advancing means may be of any desiredcharacter, we have herein shown two spiral blades 10 Xedly mounted indiametrically opposite positions within the drum. The major ortions ofthe blades 10 are curved to con lorm to a helix of relatively greatpitch so that the blades act to lift and shower the coal slightly aheadon each revolution of the drum. At the discharge end of the drum theblades 10 are given a smaller pitch so as to be more efficient asConveying elements. The drum is sealed at each end against admission ofair.

-The discharge end of the drum 7 communicates with a chamber 12 fromwhich the steam generated in the drying of the coal is conducted througha steam outlet pipe 13. The steam is preferably withdrawn under a slightvacuum.

The screw retort comprises a tubular casing or retort wall 14 supportedin vertical position. The casing 111 is preferably suspended from itsupper end, its lower end projecting slidably through a gland 15 into thechamber 12, thus accommodating changes in the diameter and length of theretort wall 14 due to temperature changes. The portion of the retortwall 14 that extends through the gland 15 is cylindrical, but theremainder of the casing 14 tapers slightly outward upwardly. Any desiredmeans may be provided to prevent the casing 14 from turning, as, forexample, straps 16 at the lower end thereof.

The retort 14 is externally heated by a furnace 17 which may be of anypreferred construction. As herein shown, it comprises desired fourcombustion chambers 18 which deliver hot gases spirally around theretort at any elevation. The hot gases pass downwardly around the retortand pass to the stack 9 through a flue 19.

lVithin the retort casing 14 is a rotor 20 comprising a tubular shaft 21(Fig. 2) having upon its periphery two spiral screw threads or fins 22.The outer diameter of the threads 22 increases upwardly from the bottomfor ease of withdrawal, such taper also affording increasing clearanceto the material being treated in the retort. It will be understood thatthe taper of the retort bore corresponds with that of the screw. Thewidt-h of the screw thread is such that a comparatively narrow spiralspace 23 is left between the shaft of the screw and the inside surfaceof the retort. A proportion of at least three inches between adjacentthread-convolutions per inch of width of thread is considered desirable.The helical thread fits inside the cylindrical retort with only a smallclearance.

The lower end of the rotor 20 is supported in a step bearing 24. Itsupper end passes through a head casting 25, a stuing box 26 preventingentrance of air.

The preheater drum 7 and the rotor 20 may be driven in any preferredmanner, as, for example, by. means of two intermeshing miter gears 27,one of said gears being driven through any desired source of power (notherein shown). The discharge ends of the blades 10`extend into thechamber 12 and sufiiciently close to the rotor 20 to feed coal to thelast-mentioned rotor, the casing 12 being of such shape as to return theupmounded coal to the screw. We believe that the plastic mass with whichthe rotor 20 almost solely deals, movesat a rate slower than eithermoist or dry coal, hence the rotor should not be completely filled atthe bottom.

The rotor 20 is internally heated by means of a heater of any preferredtype. In the present instance, we have shown a heater comprising aplurality of spaced gas burners 28 connected respectively to gas supplypipes 281. 28a are valves in the pipe 28b for regulating the intensityand points of application of the heat.

Within the head casting 25 the rotor 20 is provided with ejecting blades20a which push successive portions of the coke ribbon brought'up by thescrew thread 22 into a dust box 29. The gases and vapors driven off fromthe material in the screw-retort are withdrawn through a conduit 30connected to said dust box. Any preferred means (none being hereinshown) may be employed to divert dust from the vapor outlet 30.

The dust box 29 is located above and communicates with an annealingfurnace 31. The annealing chamber 32 of said furnace is amply taperedoutwardly and downwardly.

The annealing furnace 31 comprises fines 33 which are adapted to receivehot products of combustion from a suitable heating means (not shown),and which may be' connected to the adjacent combustion chambers 18 and."i

thus vented to the heating chamber` surrounding the screw retort, thehot gases {lon' ing eventually to the stack 9 by way of the flue 19.

The lower part 34 of the annealing chainber is preferably of metalconstruction terminating in a discharge gate 35 of any desiredcharacter, said gate being operated to .discharge coke from the lowerend of the annealer at the same rate as the annealer is filled. 36denotes a conveyor onto which the char is discharged. Any preferredmeans (none being herein shown) may be provided for gradually coolingthe coke prior to or after its discharge onto the conveyor.

The operation is as follows: The prehc'ater or drier is externallyheated to about 350 centigrade or less. The lower end of the retort Wall14 and the rotor 2O receive heat from the upper hotter parts and thusimpart heat to the coal entering the screw retort. The screw retort,being internally and externally heated, raises the temperature of eachparticle of coal at substantially the same rate. As the coal is elevatedby the screw it is subjected to a gradually increasing degree of heat,as a short distance above the point where the coal enters it meets theparts of the retort and screw which are directly heated by the furnace17 and the l internal burner 28. The temperature of the coal mass soonreaches the softening point. The particles now commence to sticktogether. The plasticity of the mass increases for a distance andfinally the particles of coal become fused to a homogeneous mass. Thefused mass soon reaches its state of maximum fluidity and then becomesincreasingly stiffer and more viscous, until it finally sets to a rigidmass. This stage from the softening point to the setting point we callthe plastic stage or zone. To prevent clogging of the rotor, theapplication of heat through- `cut the plastic zone is so controlled thatthe rotor wall is at least as hot as, or better, somewhat hotter thanthe opposite portion of the retort wall; in order that there shall be agreater tendency of the material to adhere to the retort wall than tothe rotor wall. The plastic zone may take up the entire upper portion ofthe retort above the softening point, or it may end a short distancebelow the top, depending on circumstances. The points of beginning andending of the plastie zone depend on the rate of increase oftemperature, rate of feed, rate of revolution of the screw, amount ofmoisture in the feed, and on other factors.

In the granular condition the mass ot coal, of course, lies on the uppersurface of the inner surface of the retort and the shaft of the screw.It is important, however, that the coal mass shall not completely fillthis s ace, some vacant space being left above t e coal for the escapeof the gas and vapors. Theshape of the coal mass may be described as aspiral ribbon, conforming to the helix of the screw, and several inchesthick and nearly as deep as the space between the threads. The ribbonthus has a free upper surface from which the gas and vapors arecontinuously withdrawn upwardly. By reason of such upward withdrawal,there is no condensation of vapors in or upon the cooler material lowerdown.

But as this ribbon of coal moves upward, it does not move as a simplespiral, when the motion of the individual particles is considered. Aparticle, for example, which happened to be adjacent to the thread ofthe screw on the bottom convolution, will not be found in thecorresponding position when it has reached the next convolution. We havefound that there is a continual circulation of the particles of coal.Take a particle, for example, which is in contact with the inner surfaceof the screw thread. This particle as soon as the screw commences torotate, moves inward on the upper surface of the thread until it meetsthe shaft of the screw. lt then moves upward along the vertical surfaceof the shaft until it emerges on the top surface of the ribbon of coal.Here it is again thrown outward to the inner surface of the retort.After riding along for a short distance on the top of the coal bed, itis turned under and eventually is overtaken by the upper surface of thescrew thread. llt has therefore made a complete revolution as far as thecoal bed is concerned.

The whole ribbon is thus twisting, as it were, as it climbs, the pathsof individual particles being helices whose axes are also helices, thelatter helices having substantially the same pitch as the helix of thethread. The effect of this twisting or turning over and over,4 is tobring practically eaclr particle in contact with the heated surfaces ofthe retort 14 and the screw 20. Thus the temperature of eachparticlerises at about the same rate, and all arrive at their softeningpoint at practically the same time. Each particle is in close contactwith its neighbors, and when the softening point is reached they canreadily amalgamate to form a plastic masts. lin fact, there isconsiderable pressure tending to compact the particles. This pressure isnot only due to the height of the coal bed, but also is generated by thefriction against the walls of the retort.

After the mass melts or softens this turning over and over is stillcontinued as long as the mass is plastic enough to be readily deformedby the forces actin on it, but the circulation ceases as soon as t emass stiifens suiiiciently.

It will be understood that definite temperatures can not be set down, asthese will vary with dierent coals depending on their composition. But atypical case may be described as follows: The coal is raised to itsmelting or softening point of 400 C., the method of heating being suchthat substantia-lly each particle is uniformly heated, and the wholeymass melts or softens at about the same time. The temperature is thenraised gradually to about 450 C. at which approximate temperaturesetting takes place. The colte is then held at this temperature or onesomewhat higher in the annealing chamber 32 for a further period toimprove its strength. The duration of this period depends upon thecharacter of the coal or other carbonaceous material being treat-ed.With some coals or mixtures a period of about onehalf hour gives goodresults; with others a period of one to two hours may be necessary.

By dividing the process into three stages as herein described, thecapacity of the plant per dollar of investment is increased, as thepreheater and the annealer are much less expensive than the screwretort. Moreover, the annealer 32 is more eilieient than the screwretort would be for that particular purpose, since the annealer isadapted to handle the coke with a minimum amount of friction.

llVe claim as our invention:

l. An apparatus for carbonizing coal comprising a screw-retortconsisting of a tubular casing suspended in vertical position from itsupper end and free to expand downwardly` an enlarged casing into whichthe lower end of the tubular casing extends, said last mentioned casinghaving a steam outlet, a rotary screw extending from said last mentionedcasing upwardly through said tubular casing, said tubular casing andscrew tapering slightly out upwardly, the width of the screw threadbeing approximately one-third of the distance between adjacentthread-convolutions, the screw tting the tubular casing closely wherebyto form a narrow spiral path for the material, and a ipreheater arrangedto discharge heated coal into said last mentioned casing.

2. An apparatus for carbonif/.ing coal comprising a screw ret-ortconsisting of a vertical tubular casing, an enlarged easing into whichthe lower end of the tubular casing extends, said last mentioned casinghaving a steam outlet, a rotary screw extending from said last mentionedcasing upwardly through said tubular casing, the width of the screwthread being approximately onethird of the distance between adjacentthread-convolutions. the screw fitting the tubular `casing closelywhereby to form a narrow spiral path for the material, and a preheaterarranged to discharge heated coal into said last mentioned casing.

3. An apparatus for carbonizing coal comprising a screw retortconsisting of a vertical tubular casing, an enlarged casing into whichthe lower end of the tubular casing extends, said last mentioned casinghaving a steam outlet, a rotary screw extending from said last mentionedcasing upwardly through said tubular casing, the screw fitting thetubular casing closely whereby to form a spiral path for the material, apreheater arranged to discharge heated coal into said last mentionedcasing, and means for externally heating the tubular casing and forinternally heating the screw.

4. An apparatus for carbonizing coal comprising a screw retortconsisting of a vertical tubular casing, a rotary screw within saidtubular casing, the screw thread being relatively narrow and fitting thetubular casing closely whereby to form a narrow spiral path for thematerial, means for feeding coal to the lower end of said screw retort,and an annealing furnace consisting of a chamber connected to the upperend of the screw retort tot receive coke discharged therefrom, and meansfor externally heating said chamber.

5. An apparatus for carbonizing coal comprising a vertical internallyand externally heated screw retort, a preheater arranged to dischargedried and heated coal to the lower end of the screw retort, an annealingchamber connected to the upper end of the screw retort to receive coketherefrom, and means for externally heating said chamber.

6. An apparatus for carbonizing coal comprising, in combination, a screwretort consisting of a vertical casing, an enlarged casing into whichthe lower end of said first mentioned casing extends, said enlargedcasing having a vapor outlet, a rotary screw extending from saidenlarged casing upwardly through said first mentioned casing, apreheater arranged to discharge coal into said enlarged casing, andmeans for heating said retort.

7. An apparatus for carbonizing coal comprising, in combination, a screwretort consisting of a vertical casing, an enlarged Acasing into whichthe lower end of said first mentioned casing extends, a rotary screwextending from said enlarged casing up* wardly through said firstmentioned casing,

a rotary preheater drum arranged to receive coal at one end and todischarge coal from the other end into said enlarged casing. said drumhaving a plurality of generally longitudinal helical blades on its innerperiphery to propel the coal longitudinally thereof, and means forheating said retort and said drum.

8. An apparatus for carbonizing coal comprising, in combination, a screwretort consisting of a vertical casing, an enlarged casing into whichthe lower end of said first mentioned casing extends, a rotary screwextending from said enlarged casing upwardly through said firstmentioned casing, and an elongated rotary preheater arranged to receivecoal at one end and to discharge same from the other end into saidenlarged casing, said preheater having a helical blade on its innerperiphery, the receiving end of said blade having a relatively largepitch, and the discharge end of said blade having a relatively smallpitch and extending substantially to said screw.

9. An apparatus for carbonizing coal comprising, in combination, aretort consisting of a vertical casing, an enlarged casing into whichthe lower end of said first mentioned casing extends, a rotary screwextending from said enlarged casing upwardly through said firstmentioned casing, and a preheater consisting of a furnace chamber havinga plurality of staggered transverse bafiie members, and an elongatedrotary drum journaled in said baffles, one end of said drum beingadapted to receive coal and being slidably disposed in said furnace andthe other end of said drum being adapted to discharge coal into saidenlarged chamber, and being anchored against endwise movement.

]0. An apparatus for carbonizing coal comprising a vertical screwretort, a preheater arranged to discharge dried and heated coal into thelower end of said retort, a dust chamber connected to the upper end ofsaid retort to receive coke therefrom, a vertical annealing chamberopening to the bottom of said dust chamber to receive coke therefrom,and means for externally heating said retort and said annealing chamber.

11. An apparatus for carbonizing coal comprising, in combination, avertical screw retort, a dust chamber connected to the upper end of saidscrew retort to receive coke therefrom, an annealing chamber arrangedbelow said dust chamber, an opening thereto to receive coke therefrom,and means for externally heating said retort and said annealing chamber.

12. An apparatus for carbonizing coal comprising a vertical screwretort, an enlarged downwardly tapering chamber com` municating with theupper end of said retort to receive the material discharged therefrom, avapor outlet for said chamber, an upwardly tapering vertical annealingchamber opening to the bottom of said first mentioned chamber, and meansfor externally heating said annealing chamber.

13. An apparatus for carbonizing coal comprising a furnace structurehaving. a heating space, a vertical screw retort disposed in saidheating space, means for internally heating said retort, and a verticalannealin chamber disposed in said heating space ad]acent said retort,the upper end of for internally heating said retort,la preheatl erhaving its discharge end opening to the lower end of said retort todischarge dried and heated coal thereto, and a vertical annealingchamber extending through said 15 heating space adjacent said retort,the upper end of said chamber being connected to the upper end of saidretort to receive coke therefrom. 4

In testimony whereof We have hereunto 20 aixed our signatures.

FRANK C. i GREENE. IRVING F. LAUCKS.

